• Korean Chemical Engineering Research
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• v.47 no.6
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• pp.700-704
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• 2009

A simulation study on SCR(steam carbon dioxide reforming) in gas-to-liquid(natural gas to Fischer-Tropsch synthetic fuel) process was carried out in order to find optimum reaction conditions for SCR experiment. Optimum operating conditions for SCR process were determined by changing reaction variables such as temperature and $CH_4/steam/CO_2$ feed ratio. Simulation was carried out by Aspen Plus. During the simulation, overall process was assumed to proceed under steady-state conditions. It was also assumed that physical properties of reaction medium were governed by RKS(Redlich-Kwong-Soave) equation. Optimum simulation variables such as temperature and feed ratio were determined by considering $H_2/CO$ ratio for FTS(Fischer-Tropsch synthesis), $CH_4$ conversion, and $CO_2$ conversion. Simulation results showed that optimum reaction temperature and $CH_4/steam/CO_2$ feed ratio in SCR process were $850^{\circ}C$ and 1.0/1.6/0.7, respectively. Under optimum temperature of $850^{\circ}C$, $CH_4$ conversion and $CO_2$ conversion were found to be 99% and 49%, respectively.

• Korean Journal of Clinical Pharmacy
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• v.22 no.4
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• pp.340-346
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• 2012

Background: Amphotericin B is a mainstay in the treatment of many systemic fungal infections due to its wide antifungal spectrum and low incidence of resistance. However, the use of amphotericin B is limited by its nephrotoxicity. Objectives: The objective of this study was to evaluate the incidence and risk factors of renal adverse drug reactions (ADRs) of conventional amphotericin B (Fungizone$^{(R)}$). In addition, we compared the changes of serum creatinine (SCr) between patients who remained conventional amphotericin B and patients who were switched to liposomal amphotericin B after occurrence of renal adverse reactions. Methods: Adult hospitalized patients who reported renal adverse reactions caused by conventional amphotericin B from January 2011 to July 2012 at pharmacovigilance center in Yonsei University Healthcare System included in this study. ADRs scored as 'doubtful' in Naranjo probability ADR scale were excluded. We retrospectively analyzed patients' basic clinical characteristics, concurrent diseases or nephrotoxic drugs in order to find variables that can correlate with occurrence of renal ADRs. Changes in SCr were compared between conventional amphotericin B group and liposomal amphotericin B group. Results: A total of 231 ADRs after administration of conventional amphotericin B in 75 patients were reported to pharmacovigilance center and assessed their severities as 'possible', 'probable', or 'definite'. Renal adverse reaction was the most common ADR with incidence rate of 42% (96 of 231 ADRs). Mean change in SCr from baseline was 0.26 mg/dL (change % 37.8) and statistically significant (p=0.000). Simple correlations analysis revealed that the number of concurrent diseases and number of nephrotoxic drugs were positively correlated with changes in SCr, but these results were not statistically significant. Among 43 patients who remained amphotericin B after occurrence of renal ADRs, 27 patients was administered conventional amphotericin B and 16 patients changed to liposomal amphotericin B. Mean change in SCr in amphotericin B group was 0.23 mg/dL (32.75%), whereas mean change in SCr in liposomal amphotericin B group were -0.28 mg/dL (19.38%) and difference between two groups was statistically significant (p=0.003). The numbers of patient with SCr elevation more than 30% were 9 (33.3%) in amphotericin B group and 2 (12.5%) in liposomal amphotericin B group (Odd Ratio=3.50, 95% Confidence Interval 0.65-18.85; p=0.130). Conclusion: An analysis of ADRs due to amphotericin B administration revealed significant mean changes in SCr from baseline. Switching to liposomal amphotericin B showed significant decrease in SCr compared with conventional amphotericin B.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.10
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• pp.4666-4672
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• 2011

Performance of NOx removal in SCR(Selective Catalytic Reduction) process depends on such various factors as catalyst factors (catalyst composition, catalyst form, space velocity, etc.), temperature of exhaust gas, and velocity distribution of exhaust gas. Especially the flow uniformity of gas stream flowing into the catalyst layer is believed to be the most important factor to influence the performance. In this research, the flow characteristics of a SCR process at design stage was simulated, using 3-dimensional numerical analysis method, to confirm the uniformity of the gas stream. In addition, the effects of guide vanes, baffles, and perforated plates on the flow uniformity for the inside and catalyst layer of the reactor were studied in order to optimize the flow uniformity inside the SCR reactor. It was found that the installation of a guide vane at the inlet duct L-tube part and the installation of a baffle at the upper part is very effective in avoiding chaneling inside the reactor. It was also found that additional installation of a perforated plate at the lower part of the potential catalyst layer buffers once more the flow for very uniform distribution of the gas stream.

• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.5
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• pp.118-124
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• 2011

To reach the Euro-6 regulations of PM and $NO_x$ for light-duty diesel vehicles, it will be necessary to apply the CDPF and the de-$NO_x$ catalyst. The described system consists of a catalytic configuration, where the CDPF is placed downstream of the diesel engine and followed by a urea injection unit and a urea-SCR catalyst. One of the advantages of this system configuration is that, in this way, the SCR catalyst is protected from PM, and both white PM and deposits become reduced. In the urea-SCR system, the injection control of reductant is the most important thing in order to have good performance of $NO_x$ reduction. The ideal ratio of $NH_3$ molecules to $NO_x$ molecules is 1:1 based on $NH_3$ consumption and having $NH_3$ available for reaction of all of the exhaust $NO_x$. However, under the too low and too high temperature condition, the $NO_x$ reduction efficiency become slower, due to temperature window of SCR catalyst. And space velocity also affects to $NO_x$ conversion efficiency. In this paper, rig-tests were performed to evaluate the effects of $NO_x$ and $NH_3$ concentrations, gas temperature and space velocity on the $NO_x$ conversion efficiency of the urea-SCR system. And vehicle test was performed to verify control strategy of reductatnt injection. The developed control strategy of reductant injection was improved over all $NO_x$ reduction efficiency and $NH_3$ consumption in urea-SCR system. Results of this paper contribute to develop urea-SCR system for light-duty vehicles to meet Euro-5 emission regulations.

• Applied Chemistry for Engineering
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• v.32 no.5
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• pp.516-523
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• 2021

A study using selective catalytic reduction (SCR) was conducted in conjunction with ammonia as a reducing agent for controlling nitrogen oxides, a typical secondary inducer of fine dust in the atmosphere. For NH₃-SCR experiments, a commercial catalyst of V/W/TiO₂ only and also V/W-Sb/TiO₂ catalyst with Sb were used, and phosphorous durability was confirmed. As a result of NH₃-SCR experiments, it was confirmed that the addition of Sb to V/W/TiO₂ had durability against phosphorous. In addition, the physical and chemical properties were comparatively analyzed through BET, XPS, H₂-TPR, NH₃-TPD, and FT-IR analysis. From the anaylsis results, when Sb was added to V/W/TiO₂ catalyst, P was also added resulting in the formation of SbPO₄ and the generation of VOPO₄ was suppressed. The phosphorous durability was confirmed by maintaining the redox characteristics of the catalyst before P was added.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.1
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• pp.135-144
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• 2021

In this study, we investigated the characteristics of the process of hydrogen production using boil-of gas (BOG) generated from an LNG-fueled ship and the application of hydrogen fuel cell systems as auxiliary engines. In this study, the BOG steam reformer process was designed using the UniSim R410 program, and the reformer outlet temperature, pressure, and the fraction and consumption of the product according to the steam/carbon ratio (SCR) were calculated. According to the study, the conversion rate of methane was 100 % when the temperature of the reformer was 890 ℃, and maximum hydrogen production was observed. In addition, the lower the pressure, the higher is the reaction activity. However, higher temperatures have led to a decrease in hydrogen production owing to the preponderance of adverse reactions and increased amounts of water and carbon dioxide. As SCR increased, hydrogen production increased, but the required energy consumption also increased proportionally. Although the hydrogen fraction was the highest when the SCR was 1.8, it was confirmed that the optimal operation range was for SCR to operate at 3 to prevent cocking. In addition, the lower the pressure, the higher is the amount of carbon dioxide generated. Furthermore, 42.5 % of the LNG cold energy based on carbon dioxide generation was required for cooling and liquefaction.

• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.2
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• pp.180-186
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• 2009

To meet the NOx limit without a penalty of fuel consumption, urea SCR system is currently regarded as promising NOx reduction technology for diesel engines. SCR system has to achieve maximal NOx conversion in combination with minimal $NH_3$ slip. In this study, as a basic research to develop an algorithm for urea injection control, the characteristics of engine out NOx emission and behavior of NOx reduction during steady-state and transient conditions were investigated using 2L DI diesel engine. Test results show that on increasing the catalyst temperature the variations in the outlet NOx concentration are faster and maximal allowable $NH_3$ storage exponentially decreases. For change from a low to high engine load, it can be seen that a few seconds after load-step is required to reach full NOx conversion and the adsorbed amount of $NH_3$ at lower temperature desorb during the next temperature increase, causing $NH_3$ slip. Engine out NOx emission needs to be corrected because NOx emissions just after step load is lower than that of steay state condition.

• Journal of Environmental Science International
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• v.22 no.11
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• pp.1481-1498
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• 2013

The SCR (selective catalytic reduction) system is highly-effective technique for NOx reduction from exhaust gases. In this study, the effects of the direction and size of nozzle and the ammonia injection concentration on the performance of SCR system are analyzed by using the computational fluid dynamics method. When the nozzle is arranged in zigzaged direction which is normal to exhausted gas flow, it is shown that the uniformity of gas flow and the NH3/NO molar ratio is improved remarkably. With the change of the ammonia injection concentration from 0.2 vol%(wet) to 1.0 vol%(wet), the uniformity of gas flow shows a good results. As the size of nozzle diameter changes from 6 mm to 12 mm, the uniformity of gas flow is maintained well. It is shown that the uniformity of the $NH_3/NO$ molar ratio becomes better with decreasing the ammonia injection concentration and the size of nozzle diameter.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.42 no.12
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• pp.9-12
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• 2005

This paper describes the feasibility of the electrostatic cell using carrier injection in SCR(space charge region) of PN junction. It compares the principle of the electrostatic cell's operation with the solar cell's. According to the experiment and calculation of this paper, when the cross section area of the device is $0.0001cm^2$, the device current becomes 0.15mA which is practically high enough. This paper proposes that the electrostatic cell can be used as a physical battery.

• Journal of Satellite, Information and Communications
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• v.9 no.3
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• pp.15-21
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• 2014

An electrostatic discharge (ESD) protection device, so called, N-type embedded silicon controlled rectifier (NESCR), was analyzed for high voltage operating I/O applications. A conventional NESCR standard device shows typical SCR-like characteristics with extremely low snapback holding voltage, which may cause latch-up problem during normal operation. However, our modified NESCR_CPS_PPW device with proper junction/channel engineering such as counter pocket source (CPS) and partial P-well structure demonstrates highly latch-up immune current-voltage characteristics with high snapback holding voltage and on-resistance.